1. Field of the Invention
This invention relates, generally, to a water purifying system, and more particularly relates to a reverse osmosis storage and recovery system for water purification.
2. Description of the Prior Art
Most reverse osmosis (R.O.) systems of the prior art fall into two categories: (1) those discharging product water (purified water) into an open container at atmospheric pressure, and (2) those discharging product water into a pressurized air cell tank.
The open discharge systems of category (1) are somewhat inconvenient to operate; moreover, the stored water is subject to air-borne contamination. These devices advantageously utilize total available pressure to drive water molecules through a semi-permeable R.O. membrane.
The devices of the second cateory include closed air cell tanks sealed against air-borne contamination. In these devices, however, air cell back pressure offsets incoming pressure and reduces the amount of driving force available. Consequently, both quality and quantity of product water suffer, particularly when water is drawn off and replaced in small quantities.
All R.O. systems waste a predetermined proportion of their product water production by discharging such quantity to a drain. The waste discharge carries away sediment and mineral salts leached from the product water. Unfortunately, most air cell storage systems, operating on line pressure, continually discharge the waste water even after the storage tank is filled. This results in a tremendous waste of water, shortens the life of pre-filters, and clogs waste constriction, all of which combine to cause system malfunction and concomitant customer dissatisfaction.
Examples of prior art systems are found in U.S. Pat. Nos. 3,493,496; 3,568,843; 3,542,199 and 3,726,793.
U.S. Pat. No. 3,887,463, issued June 3, 1975 to Bray, discloses an automatic valve operative to shut of all water to a R.O. system when pressure in an air cell tank reaches a predetermined pressure below incoming line pressure. The system is operative to turn on the water when pressure in the air cell tank falls below a predetermined pressure. Although this system shuts off waste water to a drain after the tank is filled, it does not prevent an increased back pressure in the air cell tank from lowering the available driving force across the R.O. membrane. It also sacrifices product water flow rate from the storage tank because of lower air cell tank back pressure. It does not have any means for automatically fast flushing the R.O. module.
U.S. Pat. No. 4,176,063, issued Nov. 27, 1979 to Tyler, discloses a R.O. system that fills a collapsible bag within a tank (squeeze tank) at a reduced back pressure. It discharges product water at near line pressure and shuts off water to the R.O. module when the tank is full. This is accomplished with a complex series of diaphragm valves. Although this prior art device accomplishes its basic objectives, it still has several shortcomings. A constriction between the waste side of the squeeze tank and the drain creates back pressure on the squeeze tank; moreover, the drain creates back pressure on the squeeze tank waste water and purified water during the filling, thereby decreasing product quantity and quality. A complex plumbing circuit and a plurality of diaphragm valves also combine to restrict product water flow when dispensing.
There is a growing need for a simpler, more effective and less expensive R.O. water purifier system.
It is the primary object of this invention to provide a water purification system of elegant design.
Another object of this invention is to provide a water purification system having a superior product water dispensing flow rate vis a vis the flow rates of prior art devices, and to provide a system having less back pressure on its storage tank when filling.
Still another object of this invention is to provide a water purification system which is less expensive to manufacture and to maintain than the systems of the prior art.